The big-band movement, periodically pronounced dead by pessimists since the 1940s, made some loud - and significant - rumblings here last weekend in an unlikely form - the new jazz of the 1970s.

In separate concerts, Sam Rivers and David Murray, two of the most important saxophonists in today's jazz, led ensembles that marvelously harnessed the free-form energies of contemporary jazz in orchestral settings.

These were not ensembles like those of Count Basie or Maynard Ferguson that play arrangements as neat as suburban lawns and sweet as a mother's lullaby.

Instead, they performed on array of material that ranged from jangling collective improvisation which rushed forward like a subway train, to lyrical passages reminiscent of birds at dusk.

The importance of the concerts can be measured partly by the musicians and seasoned jazz listeners who attended them. The Rivers concert, part of the Newport Jazz Festival-New York, on Friday night at Carnegie Hall, included in its audience pianists Ceci Taylor and Muhal Richard Abrams, drummer Steve McCall and Murray.

Writer Albert Murray, a big-band devotee since the 1920s, said after listening to David Murray (no relation) at Joseph Papp's Public Theater on Sunday night. "Now that's the kind of new jazz I like to hear. They know when to cut it off. They don't go on all night. And they're playing some interesting music."

The approaches of the Rivers and Murray groups were as different as the leaders themselves. The 14-piece Rivers orchestra, intensely disciplined and finely tuned after two months of rehearsals, moved through its music like an unstoppable juggernaut.

On the other hand, the Murray group was more ragged in ensemble passages after only four rehearsals. But its performance was more spontancous. And as an all-star dream band of the new musicians, most of whom are unkown to the general public, it included performers who are strong individuals and leaders of their own outfits (Julius Hemphill. Henry Threadgill. Fred Hopkings, James Newton, Jaki Byard, Pat Patrick).

The Murray concert also featured a scorching poetry reading by Amiri Baraka (formerly LeRoi Jones), accompanied by Murray and bassist Hopkins singer Irene Datcher's ethereal vocals and dancer Rata Christine Jones' enthusiastic but sometimes strained movements.

The father of the loft jazz movement in New York Rivers has long favored dense harmonies and elliptical melodies in his music. Both qualities were prominent in his compositions Friday night.

The band was characterized by powerful brass and rousing crescendos. One piece opened with tumultuous trumpet calls, followed by thickly-voiced collective improvisation by the whole group. And out of this cacaphony leaped Rivers, delivering a throbbing, furious tenor solo.

Besides Rivers, there were other powerful individuals in the group, particularly bartione saxophonist Hamiet Bluett, who offered several craggy solos, and drummer Warren Smith, whose billowing rolls and stacato accents underpinned the orchestra's gush of sound.

The band also included two promising young tenor saxophonists. Rickie Ford and Chico Freeman, who has not yet found their own musical personalities.

Despite its strength and attention to detail, the band suffered in three major areas: It played at the same volume level (moderately loud to loud) too much, it did not explore a variety of tone colors and the soloists did not match its ensemble power.

All these characteristics, incidentally, were presetn in the concert's first half when Rivers led a quintet in which he played lyrically on several pieces, including a bossa nova.

The Murray concert was not just focused on the unusual talents of the 23-year-old leader but the unique mix of everyone in the orchestra.

Flutist James Newton performed several virtuoso solos. Baritone saxophonixt Pat Patrick played a remarkably well-constructed solo on "Blues."

Conductor Lawrence "Butch" Morris, who directed the Murray orchestra with authority and precision, changed arrangements from performance to performance.

In the first set he directed Newton to play a serpentine solo without accompaniment. In the subsequent performance, however, he asked four saxophonists to play flute with Newton, producing a shimmering and irresistible - sound quality.

Another notable success was the detailed orchestration of "Flowers for Albert" a bleating burlesque melody Murray wrote in tribute to the late saxophonist Albert Ayler. Suggestive of a sad clown, the melody meanders in convoluted fashion, sounding like a half-dozen organ grinders going at once.

After the concert, which was recorded, Murray said. "I'm pleased with the way we played. We could have used a few more rehearsals. But I'm happy.

"I never did a big-band thing before. At the first rehearsal I was jumping up and down. I was really scared. But things turned out all right."